The present invention relates to a transmission line for high-speed electrical signal transmission. This type of transmission line is desired to enable signal transmission to be effected at increased speed with enhanced stability so as to meet the requirements for high-speed electronic computers.
It is generally recommended to employ porous substances as dielectric materials for increasing the speed in signal transmission effected by electronic devices such as transmission lines. Among such porous substances is oriented, porous, expanded polytetrafluoroethylene, produced by the method disclosed in U.S. Pat. No. 3,953,566. This material is stable both physically and chemically and has excellent electrical characteristics.
To further improve the electrical characteristics of such porous substance, the present inventor has previously invented a sheet-shaped resin material and filed an application for a patent (see the specification of Japanese Patent Laid-Open No. 176132/1982). This prior invention is arranged such that a porous sheet material is provided with a multiplicity of through-holes in order to further increase the porosity, thereby lowering the permittivity of the material. This prior art has, however, the disadvantage in that, when a porous sheet material of open-cell type is employed, the material collapses easily and is unstable. Therefore, a transmission line formed using such material has unstable characteristics, disadvantageously.
Accordingly, it is an object of the present invention to provide a high-speed transmission line having a dielectric which is not readily collapsed and has a lowered permittivity.